Lots in archives if you look for guibo (the rubber bushing with 6 bolts you mention).

Mike O94 540i, original guibo..so far

I have a 1992 E34 M50 525i. Here is some advice. Maybe something for Bruno's website. If anybody ever want to chage the following;"Universal Coupling" (you guys call it something else. This is the rubber coupling that comes between the gearbox (transmission) and the propshaft (driveshaft). It is a round rubber (donut) with 6 holes in it and connects the driveshaft with the transmission.I am going to explain the symptoms and the replacement for anybody that is interested (i suggest that you inspect this part whenever you have a moment to do so as it gets hard and disintegrates, possibly causing serious damage to tranny or driveshaft)I heard a thunk sound and then felt something hit the undercarriage. I took my foot off the eccelerator and heard and felt a fibration.I looked in the archives and found little that was usefull to explain what the problem was. I had the car on a lift at a exhaust fitment centre and saw that this coupling was nearly totally disintegrated (only iron bushings, pieces of hardened rubber and some or other kind of reinforcement "rope")Got one from the dealer ZAR589.00 = +- $71.82 @ the current exchange rate.To replace get car onto ramp or lift with backwheels off the ground (have to rotate wheels to get to bolts and nuts)Loosen all back and middle exhaust rubber mountings, with the exhaust loose remove heatshield between exhaust and undercarriage.Loosen all the bolst and nuts on the coupling and remove these bolts and nuts.With the exhaust and heatshield "out of the way", loosen the "centre bearing" on the driveshaft and bet the driveshaft to pull it out of gearbox.Remove old coupling and insert new one.Fasten the cetre bearing nuts and thereafter the nuts and bolts on the coupling. Note to replace nuts the same way you removed them. Replace heatshield and then the exhaust. Very important, if you think that the driveshaft maight have incurred some damage, have it balanced again.Hope this helps somebody with a cheap part that could cause plenty of expensive damage.